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Hi.. recently i have an assignment to compare performance and time accuracy of RTOS and an ordinary os.

I have decided to show this by runnin a program which uses a lot of system calls in it as it slows down ordinary os more than rtos.

is this approach correct ?? or is thr any other ideas .

The distinguishing feature of an RTOS is not necessarily how fast the system calls are, but how predictable they are. Usually there are certain maximum bounds on the latency of each system call. This is how QNX works. QNX also provides a guaranteed interrupt response time, which is important for devices that need their interrupts serviced in real-time.

So, I would suggest designing an experiment that shows the variability in syscall/interrupt latencies in a non-real-time OS, and conversely in a RTOS.

Generally, a RTOS tends to be slower overall because maintaining the RT property comes with an overhead. It really only means that you guarantee that an RT event is processed in at most x milliseconds.

Hi,
There are actually two types of RTOS'es soft real time and hard real time . In soft real time systems it's 'okay' not to meet the time requirement , but in hard real time systems its actually a 'must' or else system is considered a failure . RTOS's are generally used in embedded systems and they generally do only a single task , but that single task must done well , ie they are usually domain specific . I would therefore second Colonel about experiment . But you should also try to compare performance of a 'specific task' with relation to the processor / memory used compared to that of a normal operating system .

Regards
Shrek

Not quite - a Real-Time OS is by definition hard real time. Windows and Linux for example can easily provide enough responsiveness to do soft real time work for you, and they are not generally considered a real-time OS.

Hi,
I am not an authority on these things , I have read many books however , the post was more of less nearly a recollection . I might have made a mistake . But wikipedia seems to agree with me . http://wikipedia/wiki/RTOS . Anyways wishing you a happy easter .

Regards
Shrek

Have you noticed that wikipedia describes soft or hard real-time in the context of tasks.

hi,

You are *correct* . I might have developed some misconceptions due to my sloppy reading habits .

Regards
Shrek